I need to get arrow key presses, but keyDown won't call (Swift)

I am trying to build a Mac App which displays images and I want to move on to the next image when I press the right arrow key. I have looked all over stackoverflow and the internet, but just can't seem to get it.

What I tried... I tried to use keyDown(theEvent: NSEvent)but it does not call when I press any keys. I believe this is because it is not in a text field of some kind, but not sure.

What Happens... When i'm testing the program, I press a key (with keyDown function ready to println("Key Pressed")) and I get the OS X reject noise and no println to the console.

I have heard of some people subclassing NSView to override acceptsFirstResponder, but I am new to subclassing so any direction you could point me in would be great. Or if there is a way to do it w/o subclassing NSView that would be great!

Thanks in advance! Sorry for the noobness.

Solution

Subclassing is less difficult than it seems.

Short tutorial:

General assumption: keystrokes are going to be received in the view of a NSViewController subclass and to be processed in the view controller class

Create a new Cocoa Class named MyView as a subclass of NSView

Replace the contents of the created class with

import Cocoa

let leftArrowKey = 123
let rightArrowKey = 124

protocol MyViewDelegate {
  func didPressLeftArrowKey()
  func didPressRightArrowKey()
}

class MyView: NSView {

   var delegate : MyViewDelegate?

   override func keyDown(event: NSEvent) {
     let character = Int(event.keyCode)
     switch character {
     case leftArrowKey, rightArrowKey:
       break
     default:
       super.keyDown(event)
     }
   }

   override func keyUp(event: NSEvent) {
     let character = Int(event.keyCode)
     switch character {
     case leftArrowKey:
       delegate?.didPressLeftArrowKey()
     case rightArrowKey:
       delegate?.didPressRightArrowKey()
     default:
       super.keyUp(event)
     }
   }

    override var acceptsFirstResponder : Bool {
      return true
    }
  }

Change the class of the view of the ViewController in Interface Builder to MyView
In the ViewController class add the protocol MyViewDelegate- for example
```
class ViewController: NSViewController, MyViewDelegate {
```

In viewDidLoad() add

let view = self.view as! MyView
view.delegate = self
self.nextResponder = view

Implement the following delegate methods and add your code to switch the image(s)

func didPressLeftArrowKey() {
  println("didPressLeftArrowKey")
  // process keystroke left arrow
}

func didPressRightArrowKey() {
  println("didPressRightArrowKey")
  // process keystroke right arrow
}

The delegate methods are called when the appropriate arrow keys are released